1. Field of the Disclosure
The present disclosure relates to a Liquid Crystal Display (LCD) device, and more particularly, to a driving method for local dimming of an LCD device, which can be adaptively applied to the connection order of light emitting blocks of a backlight unit, and an apparatus using the same.
2. Discussion of the Related Art
Recently, flat panel displays have been popular as video displays, such as LCDs, Plasma Display Panels (PDPs), Organic Light Emitting Diodes (OLEDs), etc.
An LCD device includes a liquid crystal panel for displaying an image on a pixel matrix relying on the electrical and optical characteristics of liquid crystals that exhibit anisotropy in dielectric constant and refractive index, a driving circuit for driving the liquid crystal panel, and a backlight unit for irradiating light onto the liquid crystal panel. The gray scale of each pixel is adjusted by controlling the transmittance of light that passes from the backlight unit through the liquid crystal panel and polarizers through changing the orientation of liquid crystals according to a data signal.
In the LCD device, the luminance of each pixel is determined by the product between the luminance of the backlight unit and the light transmittance of liquid crystals that depends on data. The LCD device employs backlight dimming method for the purposes of increasing a contrast ratio and reducing power consumption. The backlight dimming method analyzes input image data and then modulates the image data and adjust a dimming value, for controlling the luminance of the backlight unit, according to the analyzed result. A Light Emitting Diode (LED) backlight unit using LEDs as light source has recently been used. The LEDs boast of high luminance and low power consumption, compared to conventional lamps. Because the LED backlight unit allow for location-based control, they may be driven by local dimming. According to the local dimming technology, the LED backlight unit is divided into a plurality of light emitting blocks and luminance is controlled on a bock-by-block basis. Local dimming may further increase the contrast ratio and decrease the power consumption since the backlight unit and the liquid crystal panel are divided into a plurality of blocks, local dimming values are decided by analyzing data on a block basis, and data is compensated based on the local dimming values.
The LCD device includes a local dimming driver (a driving chip) for driving for local dimming of the LCD device. The local dimming driver generates indexes for respective blocks to facilitate data analysis and luminance control on a block basis, and analyzes data and controls luminance according to the indexes of blocks. While it is preferable to fabricate backlight unit in such a manner that the indexes of blocks in the local dimming driver follow the block connection order of the backlight unit, the block connection order of the backlight unit does not coincide with block indexing information of the local dimming driver due to easiness in backlight fabrication and a bandwidth in which dimming data is transmitted, in most cases.
In case the block connection order of the backlight does not coincide with the indexes of blocks in the local dimming driver of the related art, a microcomputer is provided along with a backlight driver in a driver board in order to rearrange dimming values received in the order of block indexes from the local dimming driver according to the block connection order and sequentially provide the rearranged dimming values to the backlight driver. However, as many microcomputers as backlight drivers should be used, when the backlight unit is divided into at least two ports and driven on a port basis along with the trend toward a large liquid crystal panel and large backlight unit. Therefore, fabrication cost is increased. Moreover, a microcomputer for each port is capable of only converting indexes within the port, not capable of converting indexes in other ports that it is not responsible for. Accordingly, this scheme is not applicable to backlight unit with a different block connection order or a different port division structure.